Robertson County is a county located on the central northern border of Tennessee in the United States. As of the 2020 United States Census, the population was 72,803 people. Its county seat is Springfield. The county was named for James Robertson, an explorer, founder of Nashville, and a state senator, who was often called the "Father of Middle Tennessee." Robertson County is a component of the Nashville-Davidson–Murfreesboro–Franklin, TN Metropolitan Statistical Area.

Sumner County is a county located on the central northern border of Tennessee in the United States. As of the 2020 United States Census, the population was 196,281. Its county seat is Gallatin, and its most populous city is Hendersonville. The county is named after an American Revolutionary War hero, General Jethro Sumner.